The present invention relates to a portable machine for calculation or data processing.
Portable independent, and commonly electronic, machines for performing calculations or implementing functions in combination with a keyboard and a device for display of the data and results are known.
These machines are most frequently in the form of small pocket calculators, and are split into two major groups:
(1) Relatively simple machines enabling the execution of fixed programs set up during production by the manufacturer. For example, machines are currently available for performing the four basic operations of addition, subtraction, multiplication and division. Moreover, the basic functions may be accompanied by particular functions so that the machine is specialized for a given application. In particular, this is the case for mathematical or statistical functions.
(2) More complex programmable machines enabling the user himself to program the functions he requires and to store these either transiently in a provisional or temporary memory internal to the machine or on a magnetic track record carrier.
As an alternative, these machines sometimes have a passive removable device for storing specialized and fixed programs preset by the manufacturer without any possibility of development or modification by the user (e.g. Texas Instruments Model TI59).
These machines may also be equipped with an output facility leading to a hard copy printer, enabling the user to list data or programs.
For reasons of reliability and cost, all these machines are now produced based on microprocessers. In other words, they have a simplified computer structure comprising a central processing unit, a memory, and input-output channels.
The aforementioned machines have disadvantages of several kinds:
In the case of simple machines, where the instrument lacks any element for dialogue with the outside, it is impossible to secure access to personalized index cards or removable carriers, and it is impossible to implement particular functions at the user's discretion for different applications.
In the case of a programmable machine enabling the recording of programs or data on magnetic tracks, the magnetic tracks are of comparatively low capacity. Also, the magnetic track carrier is wholly passive and lacks the ability to perform functions autonomously, placing additional burden on the machine.
Furthermore, the magnetic track carrier may easily be altered or destroyed. It does not provide any security of confidentiality for the data. In also requires a comparatively expensive driving device for reading and writing.
In the case of a programmable machine having a removable carrier storing fixed programs, for practical reasons of cost and mass production considerations, they cannot be personalized.